1. Field of the Invention
This invention relates to a cross-arm mechanism in a pushbutton tuner.
2. Description of the Prior Art
Pushbuttons in general are so arranged that a setting plate mounted on a cross arm is adequately changed in its fixture angle; the movement amount of a memory slide to be urged by the setting plate is accordingly selected; and a core which is moved simultaneously with a memory slide is inserted to a given extent within a tuning coil, thereby selecting a desired frequency.
The present applicant already proposed a mechanism as shown in FIGS. 1(a), 1(b) and 1(c) as one of measures for fixing a setting plate at a desired angle on a cross arm.
Namely, on a cross arm 1 is secured a setting pin 2 and the setting pin 2 pivotally supports a setting plate 3 which is engaged therewith. The setting plate 3 is arc-shaped at one end thereof nearer to the front end of the cross arm, and triangular at the other end thereof nearer to the proximal end of the cross arm 1, respectively. That is, it is drop-shaped as a whole. At the side edge of said other end of the setting plate 3 is formed an urging protuberance 4 for urging a memory slide.
A substantially U-shaped plate spring 5 is mounted on the cross arm 1 in a manner surrounding the setting plate 3. The plate spring 5 is fixed at the front end thereof to the front end of the cross arm 1. The two legs, right and left, of the U-shape extend toward the proximal end of the cross arm 1 in a manner grasping the setting plate 3 from right and left directions. Further, the plate spring 5 has a circular tightening portion 6 at inner sides of the legs near the tip of the plate spring 5. The tightening portion 6 surrounds and contacts a front end portion of the setting plate 3 which is correspondingly configured in a circle.
A pushbutton 7 is coupled to the proximal end of the cross arm 1 and the proximal ends of the right and left legs of the plate spring 5. Fastening protuberances 7a of the pushbutton 7, when the pushbutton 7 is fully engaged with the cross arm 1, inwardly urge the right and left legs to tighten the legs, while when the pushbutton 7 is halfway pulled out of the cross arm 1, the urging force by the fastening protuberances 7a is released to thereby permit the right and left legs of the plate spring 5 to expand outward.
This cross arm mechanism functions as will be described hereunder.
To preset a frequency to be selected by a pushbutton, a tuning shaft associated with the pushbutton is previously rotated by hand to move the associated core which is moved simultaneously with rotation of the tuning shaft to a given extent within the associated tuning coil, thereby selecting a frequency to be set at the pushbutton. With this operation, a memory slide 8 which is movable simultaneously with the core means longitudinally and reaches a position corresponding to the frequency to be selected. Thereafter, the pushbutton 7 which is coupled to the proximal ends of the cross arm 1 and the plate spring 5 is halfway pulled out of them to release the fastening force against the plate spring 5. Then, the tightening portion 6 of the plate spring 5 expands outwardly and permits the front portion of the setting plate 3 to freely rotate about the setting pin 2.
When the pushbutton 7 and the cross arm 1 are pushed in the tuner, the urging protuberance 4 of the setting plate 3 gets in contact with a V-like cut-in 9 of the memory slide 8 and is guided by a sloping edge of the V-like cut-in 9 to reach the summit of the same. In this case, since the position of the summit of the V-like cut-in 9 is determined by the position of the memory slide 8, which corresponds to the position of the depth of the core within the tuning coil, the setting plate 3 rotates about the setting pin 2 so that the urging protuberance 4 reaches the summit of the V-like cut-in 9.
After the angle of the setting plate 3 is fixed to meet the summit of the V-like cut-in 9 of the memory slide 8, the pushbutton 7 at the proximal end of the cross arm 1 is further pushed in the tuner. At that time, since the cross arm 1 is prevented from advancing due to the memory slide 8, only the pushbutton 7 slides on the cross arm 1 to be thereby fully engaged with the cross arm 1. In this case, the proximal ends of the legs of the plate spring 5 are inwardly urged by the fastening protuberances 7a of the pushbutton 7 and are tightened narrower so as to strongly fasten the front portion of the setting plate 3. As the result, the setting plate 3 is fixed unmoved on the cross arm 1 with an angle corresponding to the position of the V-like cut-in 9 of the memory slide 8.
After that, the urging protuberance 4 of the setting plate 3 which was fixed on the cross arm 1 contacts the cut-in 9 whenever the pushbutton 7 is pushed in the tuner to shift the memory slide 8 and insert the core which moves simultaneously with the memory slide 8 to the given extent within the coil.
Pushbuttons in general are further so arranged that, upon selection of a frequency by pushing a given pushbutton in, a clutch mechanism which is provided between the pushbutton and a tuning shaft is actuated to attach the pushbutton and the tuning shaft in order not to apply the load of the tuning shaft to the pushbutton. To detach the connection of the pushbutton and the tuning shaft in response to pushing operation of the pushbutton, one conventional mechanism uses a kick arm K intersecting with the cross arms 1 of the pushbuttons as shown in FIG. 1(b). The kick arm K moves longitudinally of the pushbutton tuner when the pushbutton is pushed in because a tapered projection 7b of the kick arm K is urged by an urging protuberance 7c formed within the pushbutton, thereby attaching said connection. The kick arm K is returned to its original position due to a spring force when the pushing operation of the pushbutton is finished to thereby connect the pushbutton and the tuning shaft again.